The present invention relates to integrated circuit (IC) packages and, more particularly, to a heat spreader for package-on-package (PoP) type packages.
A conventional PoP device has top and bottom packaged devices, for example where the bottom packaged device is a processor and the top packaged device is a memory. The top and bottom packages may be assembled by different manufacturers and then the PoP device assembled by a third party. PoP devices are useful because they provide the third party the flexibility to match a particular processor with any one of a variety of compatible memory modules while reducing the footprint of the combined package, which is the footprint of the bottom package. In contrast, conventional stacked-die packages, which combine a processor and one or more memory modules in one integrated package, offer a similarly reduced footprint, but without the ability to combine devices from separate manufactures and without the ability to use known good devices.
FIG. 1 is a cross-sectional side view of a conventional PoP package 100. The PoP package 100 comprises a bottom package 101, a top package 102, and an interposer 103, which are generally square-shaped when viewed from above (not shown). The bottom package 101 comprises a processor die 104 electrically and adhesively connected to a substrate 105 via, respectively, conductive balls 106 and an underfill 107. The underfill 107 may include a die-attach material. The substrate 105 is a redistribution layer comprising die contact pads 108, PoP contact pads 109, bottom contact pads 110, filler 111, and conductive paths 112. The conductive paths 112 electrically interconnect corresponding die contact pads 108, PoP contact pads 109, and/or bottom contact pads 110. The conductive paths 112 and the contact pads 108 and 110 are metallic, while the filler 111 is a non-conductive dielectric material. The conductive balls 106 are physically and electrically connected to the corresponding die contact pads 108. Package conductive balls 113 are physically and electrically connected to corresponding bottom contact pads 110.
The top package 102 comprises two memory dies 120, with the die 120(1) stacked on top of the die 120(2). The die 120(2) is attached to a substrate 121. Each die 120 is wire bonded to corresponding contacts 122 on the top of the substrate 121 via wires 123. The dies 120, the wires 123, and the top of the substrate 121 are encapsulated with an encapsulant 124. The contacts 122 connect to bottom contacts pads 125 using vias 126 through the substrate 121. The bottom contact pads 125 are arranged in a plurality of concentric rectangles around the periphery of the bottom of the substrate 121 of the top package 102. A set of conductive balls 127 is attached to the bottom contact pads 125.
The interposer 103 connects the bottom contact pads 125 of the top package 102 to the PoP contact pads 109 of the bottom package 101 via the conductive balls 127 and 130. The interposer 103 comprises (i) a plurality of top contact pads 131 that correspond to the bottom contact pads 125 of the top package 102 and the conductive balls 127, (ii) a plurality of bottom contact pads 132 that correspond to the PoP contact pads 109 of the bottom package 101 and the conductive balls 130, (iii) a filler 133, and (iv) conductive paths 134 connecting the top contact pads 131 to the corresponding bottom contact pads 132. The conductive paths 134 and contacts pads 131 and 132 are metallic, while the filler 133 is a non-conductive dielectric material. A number of conductive balls 130—corresponding to the bottom contact pads 132 of the interposer 103 and the PoP contacts pads 109 of the bottom package 101—are connected to the bottom contact pads 125.
When the PoP package 100 is assembled, (i) the conductive balls 130 of the interposer 103 are connected—e.g., using a reflow process—to the corresponding PoP contact pads 109 of the bottom package 101 and (ii) the conductive balls 127 of the top package 102 are connected—e.g., using the same or different reflow process—to the corresponding top contact pads 131 of the interposer 103. Once the PoP package 100 is assembled, the die 104 of the bottom package 101 communicates with (i) the dies 120 of the top package 102 via the interposer 103 and (ii) external components (not shown) via the conductive balls 113.
In operation, the die 104 generates heat which, if excessive, may damage itself and/or other components of the PoP package 100.